What does Enhanced Geothermal System (EGS) mean?
An Enhanced Geothermal System is where the hot rocks which contain the geothermal energy do not have a naturally water saturated permeable reservoir. In an EGS the permeable reservoir has to be engineered. This is done either by: (1) hydraulic fracture stimulation to open up natural fractures or zones of weakness in the rock via injection of water under high pressure into the rocks or (ii) injection of acid in the rock to dissolve minerals to enhance the rock permeability along existing fracture zones having acid soluble minerals. Water then can flow or be pumped through these fractures and zones to collect the heat from the hot rocks. An EGS system is sometimes known as Hot Fractured Rocks (HFR). This is sometimes used where hydraulic fracture stimulation is used to enhance the permeability in hot dry rocks with no open fractures or in rocks which have open fractures which are water saturated.
